Cannot equip any unique or Chaos legs. Definitely for my class and tried with several different items. Restarted game and PC.
Any help appreciated.
Hello,
Unequip the existing version of the unique you are trying to equip with.
The “you can not equip the same item twice" message should have made you guess the “bug" 
Thank you for your reply.
I have unequipped and then tried to equip uniques. Non uniques equip fine.
I have never had the message you referred to.